1. Field of the Invention
The present invention relates generally to pumps and more specifically to a pump for implantation into the human body.
2. Description of the Prior Art
In the field of fluid delivery systems for use in the human body, the present devices are either not wholly implantable or the devices are not directly controllable or capable of preventing blow-through caused by pressure applied to the inlet of the pump. The latter feature is necessary to insure that potentially dangerous over-doses of drugs or hormones are not inadvertently forced into the host by sudden pressure on the reservoir, as might be caused by a blow.
Prior U.S. Pat. No. 3,963,380, to which reference is made, describes the concepts and advantages of a piezoelectric disk bender for powering micro-pumps. Briefly, that pump and the diaphragm pump of this invention employ a piezoelectric variable volume chamber and a solenoid controlled valve arrangement operated in sequence to pump small volumes of liquid. The sequence is produced by developing a phase difference between the control of the piezoelectrical chamber and the solenoid valve arrangement.
According to the practice of this invention, it has been found possible to convert the micro-pump described by U.S. Pat. No. 3,963,380 into a diaphragm pump and to obtain superior results thereby.
One difficulty discovered in the specific embodiment described by U.S. Pat. No. 3,963,380 is that the pump turned out to be sensitive to the presence of any gas bubbles in the medium being pumped. The bubbles could accumulate in the pump, and, on occasion, the pump might become gas bound.
In addition, the micro-pump of the earlier invention requires, relatively speaking, a large quantity of pumped medium inside the pump system. Priming the pump requires considerable care.